Five-ring fused heteroaromatic compounds and conjugated polymers thereof

ABSTRACT

Compounds having a core comprised of an aromatic ring and at least two annulated beta-substituted fused thiophene ring systems of the general formula:
 
-(β-R 2 —FT2ArFT2-β-R 2 )—,
 
and polymers or copolymers thereof, of the general formulas:
 
-{-β-R 2 —FT2ArFT2-β-R 2 )-G 1 -} n -, or
 
-{-G 1 -(β-R 2 —FT2ArFT2-β-R 2 )-G 1 -G 2 -} n -,
 
where β-R 2 —FT2ArFT2-β-R 2 , -G 1 -, -G 2 -, and n are as defined herein. Also disclosed are compositions, articles, or devices comprising the polymers, and methods for making and using the polymers. The compositions, articles, or devices can be used, for example, for electronic applications, such as light emitting devices and semiconductor devices.

The entire disclosure of any publication or patent document mentionedherein is incorporated by reference.

BACKGROUND

The disclosure generally relates to compounds and polymers having a corecomprised of an aromatic ring and annulated fused thiophenes, tocompositions, to articles, and to methods for making and using thecompounds and polymers.

SUMMARY

The disclosure provides compounds and polymers having a five-ring fusedheteroaromatic core comprised of an aromatic ring and annulatedbeta-substituted fused thiophenes, to compositions, to articles, and tomethods for making and using compounds and polymers that can be used,for example, for electronic applications, such as light emitting devicesand semiconductor devices, and methods of making and using the compoundsand polymers.

BRIEF DESCRIPTION OF DRAWINGS

In embodiments of the disclosure:

FIG. 1 shows known examples of substituted and unsubstituted three-ringfused heteroaromatics related to the disclosure.

FIG. 2 shows known examples of semiconductor polymers incorporating thethree-ring fused heteroaromatics of FIG. 1.

FIG. 3 shows an example of Applicant's prior high performancesemiconductor polymer P2TDC13FT4 and a partial synthetic route.

FIG. 4 shows example syntheses of a class of α-, α′-unsubstituted, β,β′-alkyl substituted five-ring fused ring heteroaromatics of the formula2 and 2′.

FIG. 5 shows an example of a known route to an α-, α′-alkyl substitutedfive-ring fused ring heteroaromatic compound of the formula A.

FIG. 6 shows an example route to α-, α′-unsubstituted, β-, β′-alkylsubstituted five-ring fused ring heteroaromatics of formula 2a.

FIG. 7 shows an example of a route to semiconducting polymers offormulas 4 and 5 containing α-, α′-aromatic ring substituted, β-,β′-alkyl substituted five-ring fused ring heteroaromatic cores.

FIG. 8 shows an example of a route to a semiconducting polymer of theformula 4a.

FIG. 9 shows an example of an unsuccessful synthesis of an α-, α′-alkylsubstituted five-ring fused ring heteroaromatic of the formula 3a.

FIG. 10 shows example UV-vis solution spectra for a compound of FIG. 6of the formula 2a having β-, β′-C₁₇H₃₅ substituents, and the knownDC17FT4 having β-, β′-C₁₇H₃₅ substituents.

FIG. 11 shows examples of solution and solid UV-vis absorption spectraof the semiconducting polymer of formula 4a in FIG. 8.

FIG. 12 illustrates reorganization energy and the transfer integral inthe charge carrier mobility as deduced from modeling.

FIG. 13 illustrates the internal reorganization energy for hole transferas a function of various internal reorganization components (λ=λ₀+λ₊)and the ionization potential (IP=E^(*) ₊−E) as deduced from modeling.

FIG. 14 provides Table 1 that lists Hole Reorganization Energiesobtained from modeling for selected fused core model compounds.

DETAILED DESCRIPTION

Various embodiments of the disclosure will be described in detail withreference to drawings, if any. Reference to various embodiments does notlimit the scope of the invention, which is limited only by the scope ofthe claims attached hereto. Additionally, any examples set forth in thisspecification are not limiting and merely set forth some of the manypossible embodiments for the claimed invention.

DEFINITIONS

“Unit,” “polymerizable unit,” or like terms in the context of thedisclosed polymers or copolymers refer to the number of different coreunits and like other conjugated units within a discrete repeat segment(n) of a polymer or copolymer, see for example the core unit having acore comprised of a central aryl or aromatic ring (Ar) and at least twooppositely situated annulated beta-substituted fused thiophenes(β-R₂—FT2) of the general representation β-R₂—FT2ArFT2-β-R₂, and atleast one non-fused backbone aryl or heteroaryl unit(s), -(Ar)_(m)-,where m is from 1 to about 6, comprised of, for example, one or more-G₁-, -G₂-, or -G₁-G₂-G₁-, and combinations thereof, such as polymers orcopolymers of the general formulas:-{-(core)-(Ar)_(m)-}_(n) or-{-β′-R₂—FT2ArFT2-β-R₂)-(Ar)_(m)-}_(n),such as-{-(β-R₂—FT2ArFT2-β-R₂)-G₁-}_(n)-, and-{-G₁-β-R₂—FT2ArFT2-β-R₂)-G₁-G₂-}_(n)—, or-{-(β-R₂—FT2ArFT2-β-R₂)-G₁G₂G₁-}_(n)-.

In embodiments, a repeat unit or segment (n) can have one or more likecore units and one or more additional conjugated units (i.e., G₁,-G₁-G₂-) within a discrete repeat segment of a polymer.

“Hydrocarbon,” “hydrocarbyl,” “hydrocarbylene,” “hydrocarbyloxy,” andlike terms refer to monovalent such as —R, or divalent —R— moieties, andcan include, for example, alkyl hydrocarbons, aromatic or arylhydrocarbons, alkyl substituted aryl hydrocarbons, alkoxy substitutedaryl hydrocarbons, heteroalkyl hydrocarbons, heteroaromatic orheteroaryl hydrocarbons, alkyl substituted heteroaryl hydrocarbons,alkoxy substituted heteroaryl hydrocarbons, and like hydrocarbonmoieties, and as illustrated herein.

“Alkyl” includes linear alkyls, branched alkyls, and cycloalkyls.“Substituted alkyl” or “optionally substituted alkyl” refers to an alkylsubstituent, which can include, for example, a linear alkyl, a branchedalkyl, or a cycloalkyl, having from 1 to 4 optional substituentsselected from, for example, hydroxyl (—OH), halogen, amino (—NH₂ or—NR₂), nitro (—NO₂), acyl (—C(═O)R), alkylsulfonyl (—S(═O)₂R), alkoxy(—OR), and like substituents, where R of the optional substituent can bea hydrocarbyl, aryl, Het, or like moieties, such as a monovalent alkylor a divalent alkylene having from 1 to about 10 carbon atoms. Forexample, a hydroxy substituted alkyl, can be a 2-hydroxy substitutedpropylene of the formula —CH₂—CH(OH)—CH₂—, an alkoxy substituted alkyl,can be a 2-methoxy substituted ethyl of the formula —CH₂—CH₂-β-CH₃, anamino substituted alkyl, can be a 1-dialkylamino substituted ethyl ofthe formula —CH(NR₂)—CH₃, an oligo-(oxyalkylene), poly-(oxyalkylene), orpoly-(alkylene oxide) substituted alkyl, can be, for example, of thepartial formula —(R—O)_(x)—, where x can be, for example, from 1 toabout 50, and from 1 to about 20, and like substituted oxyalkylenesubstituents, such as of the formula —(CR⁵—CHR⁵—O)_(x)— where R⁵ ishydrogen or a substituted or unsubstituted (C₁₋₈) hydrocarbyl such asalkyl, and x is an integer of from 1 to about 50.

“Aryl” includes a mono- or divalent-phenyl radical, or an ortho-fusedbicyclic carbocyclic radical having about nine to twenty ring atoms inwhich at least one ring is aromatic. Aryl (Ar) can include substitutedaryls, such as a phenyl radical having from 1 to 5 substituents, forexample, alkyl, alkoxy, halo, and like substituents. An “Aryl” coreincludes a substituted or unsubstituted (i.e., in the 1- and4-positions, while the 2,3- and 5,6-positions are, respectively,heteroaryl substituents such the FT2 groups), bis-annulated,bis-ortho-fused phenyl radical, or an ortho-fused bicyclic carbocyclicradical having about nine to twenty ring atoms in which at least onering is aromatic. Aryl (Ar) substituents or cores can includesubstituted or unsubstituted, heteroaryls or heterocyclics.

“Het” includes a four-(4), five-(5), six-(6), or seven-(7) memberedsaturated or unsaturated heterocyclic ring having 1, 2, 3, or 4heteroatoms selected from the group consisting of oxy, thio, sulfonyl,sulfonyl, selenium, tellurium, and nitrogen, which ring is optionallyfused to a benzene ring. Het also includes “heteroaryl,” whichencompasses a radical attached via a ring carbon of a monocyclicaromatic ring containing five or six ring atoms consisting of carbon and1, 2, 3, or 4 heteroatoms each selected from the group consisting ofnon-peroxide oxy, thio, and N(X) wherein X is absent or is H, O,(C₁₋₄)alkyl, phenyl, or benzyl, and a radical of an ortho-fused bicyclicheterocycle of about eight to ten ring atoms derived therefrom,particularly a benzo-derivative or one derived by fusing a propylene,trimethylene, or tetramethylene diradical thereto. A particularly usefulAryl (Ar) backbone moiety includes substituted or unsubstituted,divalent thiophene.

In embodiments, halo or halide includes fluoro, chloro, bromo, or iodo.Alkyl, alkoxy, etc., include both straight and branched groups; butreference to an individual radical such as “propyl” embraces only thestraight chain radical, a branched chain isomer such as “isopropyl”being specifically referred to.

The carbon atom content of various hydrocarbon-containing (i.e.,hydrocarbyl) moieties can alternatively be indicated by a prefixdesignating a lower and upper number of carbon atoms in the moiety,i.e., the prefix indicates a moiety of the integer “i” to the integer“j” carbon atoms, inclusive. Thus, for example, C₁ to C₈ alkyl,(C₁-C₈)alkyl, or C₁₋₈alkyl refers to an alkyl of one to eight carbonatoms, inclusive, and hydrocarbyloxy such as (C₁-C₈)alkoxy or C₁₋₈alkoxyrefers to an alkoxy radical (—OR) having an alkyl group of one to eightcarbon atoms, inclusive. In another example, C₁ to C₄₀ alkyl,(C₁-C₄₀)alkyl, (C₁₋₄₀) alkyl, or C₁₋₄₀alkyl refers to an alkyl of one toforty carbon atoms, inclusive, and hydrocarbyloxy such as (C₁-C₄₀)alkoxyor C₁₋₄₀alkoxy refers to an alkoxy radical (—OR) having an alkyl groupof one to forty carbon atoms, inclusive.

Specifically, C₁₋₈alkyl can be, for example, methyl, ethyl, propyl,isopropyl, butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, 3-pentyl,hexyl, heptyl, or octyl; (C₃₋₁₂)cycloalkyl can be cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc.,including bicyclic, tricyclic, or multi-cyclic substituents, and likesubstituents.

A specific “hydrocarbyl” can be, for example, (C₁₋₄₀)hydrocarbyl,including all intermediate chain lengths and values. Preferred“hydrocarbyl” groups can be, for example, those R₁ and R₂ groups whichcan impart enhanced solubility to the monomer or co-monomer startingmaterials, or to the resulting polymers, such as (C₁₆)hydrocarbyl,(C₁₇)hydrocarbyl, (C₁₈)hydrocarbyl, (C₂₀)hydrocarbyl, (C₂₂)hydrocarbyl,(C₂₄)hydrocarbyl, (C₂₆)hydrocarbyl, (C₂₈)hydrocarbyl, (C₃₀)hydrocarbyl,(C₃₂)hydrocarbyl, (C₃₄)hydrocarbyl, (C₃₆)hydrocarbyl, (C₃₈)hydrocarbyl,(C₄₀)hydrocarbyl, including all intermediate chain lengths and values,and mixtures thereof, for example, (C₁₆₋₄₀)hydrocarbyl,(C₂₀₋₄₀)hydrocarbyl, (C₂₂₋₃₆)hydrocarbyl, (C₂₂₋₄₀)hydrocarbyl, and(C₂₆₋₄₀)hydrocarbyl, (C₃₀₋₄₀)hydrocarbyl.

C₁₋₈alkoxy can be, for example, methoxy, ethoxy, propoxy, isopropoxy,butoxy, iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, hexyloxy,1-methylhexyloxy, heptyloxy, octyloxy, and like substituents.

H—C(═O)(C₃₋₇)alkyl- or —(C₂₋₇)alkanoyl can be, for example, acetyl,propanoyl, butanoyl, pentanoyl, 4-methylpentanoyl, hexanoyl, orheptanoyl. Aryl (Ar) can be, for example, phenyl, naphthyl, anthracenyl,phenanthrenyl, fluorenyl, tetrahydronaphthyl, or indanyl. Het can be,for example, pyrrolidinyl, piperidinyl, morpholinyl, thiomorpholinyl, orheteroaryl. Heteroaryl can be, for example, furyl, imidazolyl,triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl,pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide),thienyl, pyrimidinyl (or its N-oxide), indolyl, isoquinolyl (or itsN-oxide), or quinolyl (or its N-oxide).

A specific value for Het includes a five-(5), six-(6), or seven-(7)membered saturated or unsaturated ring containing 1, 2, 3, or 4heteroatoms, for example, non-peroxide oxy, thio, sulfinyl, sulfonyl,selenium, tellurium, and nitrogen; and a radical of an ortho-fusedbicyclic heterocycle of about eight to twelve ring atoms derivedtherefrom, particularly a benzo-derivative or one derived by fusing apropylene, trimethylene, tetramethylene, or another monocyclic Hetdiradical thereto.

Other conditions suitable for formation and modification of thecompounds, oligomers, polymers, composites or like products of thedisclosure, from a variety of starting materials or intermediates, asdisclosed and illustrated herein, are available. For example, see Feiserand Feiser, “Reagents for Organic Synthesis”, Vol. 1, et seq., 1967;March, J. “Advanced Organic Chemistry,” John Wiley & Sons, 4^(th) ed.1992; House, H. O., “Modem Synthetic Reactions,” 2^(nd) ed., W. A.Benjamin, New York, 1972; and Larock, R. C., “Comprehensive OrganicTransformations,” 2^(nd) ed., 1999, Wiley-VCH Publishers, New York. Thestarting materials employed in the preparative methods described hereinare, for example, commercially available, have been reported in thescientific literature, or can be prepared from readily availablestarting materials using procedures known in the field or provided inthe working examples. It may be desirable to optionally use a protectinggroup during all or portions of the above described or alternativepreparative procedures. Such protecting groups and methods for theirintroduction and removal are known in the art. See Greene, T. W.; Wutz,P. G. M. “Protecting Groups In Organic Synthesis,” 2^(nd) ed., 1991, NewYork, John Wiley & Sons, Inc.

“Include,” “includes,” or like terms means encompassing but not limitedto, that is, inclusive and not exclusive.

“Monomer,” “mer,” or like terms refer to a compound that can be (or hasalready been) covalently combined or linked with other monomers of likeor different structure to form homogenous (homopolymers) orheterogeneous (e.g., copolymers, terpolymers, and like heteropolymers)chains of the target polymer. “Polymer” or like terms includescopolymers. Suitable monomers as disclosed and illustrated herein caninclude, for example, low molecular weight polymerizable compounds, suchas from about 50 to about 200 Daltons, and higher molecular weightcompounds, such as from about 200 to about 10,000 Daltons, includingdivalent or bifunctionally reactive compounds as disclosed herein, suchas di-tin fused thiophene compounds, di-halogen thiophene compounds,di-halogen oligo-thiophene compounds, and like compounds.

“About” modifying, for example, the quantity of an ingredient in acomposition, concentrations, volumes, process temperature, process time,yields, flow rates, pressures, and like values, and ranges thereof,employed in describing the embodiments of the disclosure, refers tovariation in the numerical quantity that can occur, for example: throughtypical measuring and handling procedures used for making compounds,compositions, composites, concentrates or use formulations; throughinadvertent error in these procedures; through differences in themanufacture, source, or purity of starting materials or ingredients usedto carry out the methods; expressing measured polymer number average orweight average molecular weight properties, and like considerations. Theterm “about” also encompasses amounts that differ due to aging of acomposition or formulation with a particular initial concentration ormixture, and amounts that differ due to mixing or processing acomposition or formulation with a particular initial concentration ormixture. The claims appended hereto include equivalents of these “about”quantities.

“Consisting essentially of” in embodiments refers, for example, to acompound, to a polymer or copolymer composition, to a method of makingor using the compound, the polymer, the copolymer, a formulation, orcomposition, and articles, devices, or any apparatus of the disclosure,and can include the components or steps listed in the claim, plus othercomponents or steps that do not materially affect the basic and novelproperties of the compositions, articles, apparatus, or methods ofmaking and use of the disclosure, such as particular reactants,particular additives or ingredients, a particular agent, a particularmonomer, co-monomer, or condition, or like structure, material, orprocess variable selected. Items that may materially affect the basicproperties of the components or steps of the disclosure or that mayimpart undesirable characteristics to the present disclosure include,for example, premature polymer chain termination, excessivecrosslinking, extended or unnecessary exposure of the resulting polymerto excessively high temperatures, and like contrary steps.

The indefinite article “a” or “an” and its corresponding definitearticle “the” as used herein means at least one, or one or more, unlessspecified otherwise.

Abbreviations, which are well known to one of ordinary skill in the art,may be used (e.g., “h” or “hr” for hour or hours, “g” or “gm” forgram(s), “mL” for milliliters, and “rt” for room temperature, “nm” fornanometers, and like abbreviations).

Specific and preferred values disclosed for components, reactants,reagents, ingredients, additives, initiators, metal catalysts, crosslinkers, and like aspects, and ranges thereof, are for illustrationonly; they do not exclude other defined values or other values withindefined ranges. The compositions and methods of the disclosure includethose having any value or any combination of the values, specificvalues, more specific values, and preferred values described herein. Anyaspect, feature, or embodiment recited in the appended claims can beused in any combination or permutation with any one or more otheraspect, feature, or embodiment recited in the appended claims.

Organic semiconducting compounds (OSC), including oligomers andpolymers, have been the focus of academic and industrial researchbecause of their interesting electronic and optoelectronic properties.These organic materials have a variety of applications including organicthin film transistors (OTFTs), organic light-emitting diodes (OLEDs),and electro-optic (EO) applications. Fused aromatics and theiroligomeric and polymeric derivatives have been widely used as valuableorganic thin film transistors due to their good pi-stacking in the solidstate, good thermal stability, and high device performance. Althoughthree-ring fused hetero-aromatics having a middle phenyl ring and twoexternal thiophene rings (FIG. 1) were discovered more than 30 years ago(see Hebert, M., et al., Preparation of2,3-[di(2-thienyl)butane-2,3-diol and 4,8-dimethylbenzo[1,2-b;4,5,-b′]dithiophene,” Comptes Rendus des Seances de l'Academie desSciences, Serie C: Sciences Chimiques (1971), 273(14), 825-8; Caullet,C., et al., “Identification of a product obtained by the electrochemicalreduction of 2-acetylthiophene in an acid medium in awater-tetrahydrofuran mixture,” Comptes Rendus, Serie C: SciencesChimiques, (1967), 264(2), 228-31), only recently have they been used asthe repeat unit in semiconductor polymers (FIG. 2) (see for example,Pan, H., et al., “Low-Temperature, Solution-Processed, High-MobilityPolymer Semiconductors for Thin-Film Transistors,” J. Am. Chem. Soc.,(2007), 129(14), 4112-4113; Ong, B., et al., “Electronic devicescomprising poly(dithienyl-benzodithiophenes) as semiconductors,” EP1916250; Pan, H., et al., “Benzodithiophene copolymer—a low-temperature,solution-processed high-performance semiconductor for thin-filmtransistors,” Advanced Functional Materials, (2007) 17(17), 3574-3579;Li, Y., et al., “Functionalized heteroacenes and polymers,” U.S. Pat.Appl. Publ. US 2007260069; Li, Y., et al.,“Poly[bis(ethynyl)heteroacene]s and electronic devices generatedtherefrom,” U.S. Pat. Appl. Publ. US 2007235726; and Heeney, M., et al.,“Polybenzodithiophenes useful for semiconductors or charge transportmaterials in optical, electro-optical or electronic devices,” U.S. Pat.Appl. Publ. US 2005082525). These high performance semiconductingpolymers 1 have a field-effect mobility larger than 0.1·cm²/V·s.Comparison of published research results also indicated that feweraromatic protons in the semiconductor polymers provided greater thermalstability to the polymers. Our previous high performance fused thiophenepolymers (prepared as shown in FIG. 3) have high thermal stability inair due to the absence of aromatic protons in their fused thiophene ringcore (see also Fong, H.-H., et al., “Tetrathienoacene Copolymers As HighMobility, Soluble Organic Semiconductors,” J. Am. Chem. Soc., (2008),130(40), 13202-13203).

In embodiments, the disclosure provides a group of α-, α′-un-substitutedfive-ring fused heteroaromatic compounds, including small molecules,oligomers, and polymers thereof, having a central phenyl ring and atotal of four fused or annulated thiophene rings to provide a class ofcompounds having the general core structure of formula 2 or 2′ in FIG.4.

In embodiments, the disclosure also provides a synthetic method to makethe aforementioned α-, α′-un-substituted five-ring fused hetero-aromaticcompounds having the general core structure of formula 2 also shown inFIG. 4.

A recent publication described the synthesis of α-, α′-alkyl (or aryl)substituted five-ring fused heteroaromatics having compounds with a corestructure of the formula A in FIG. 5 (see Kastler, M., et al. “Highperformance solution processible semiconductor based ondithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene,” WO 2010000670).The last step of ring closure to form the targeted five-ring fusedhetero aromatic in FIG. 5 provided yields of 26% to 43% even though theα-position of thiophene was protected by an alkyl side chain. Onecomplication in this last step is the possibility of intermolecularpolymerization (see Sirringhaus, H., et al.,“Dibenzothienobisbenzothiophene a novel fused-ring oligomer with highfield-effect mobility,” Journal of Materials Chemistry (1999), 9(9),2095-2101).

Recently, there has been an interest in synthesizing semiconductorpolymers for organic electronic applications (see for example, Kastler,M., et al., Polybenzothiophene polymers and process for theirpreparation and their use as semiconductors or charge transportmaterials,” WO 2010018081; Liu, M., et al., “A Polymer with aBenzo[2,1-b; 3,4-b′]dithiophene Moiety for Photovoltaic Applications,”ChemSusChem, (2010), 3(1),106-111; Kastler, M., et al.,“Poly(5,5′-bis(thiophen-2-yl)-benzo[2,1-b; 3,4-b′]dithiophene) and itsuse as high performance solution processible semiconducting polymer,” WO2010000669; Kastler, M., et al., “Solution-processible semiconductingdonor-acceptor copolymers,” WO 2010000755; Rieger, R., et al., “RationalOptimization of Benzo[2,1-b; 3,4-b′]dithiophene-Containing Polymers forOrganic Field-Effect Transistors,” Advanced Materials (Weinheim,Germany) (2010), 22(1), 83-86, ISSN:0935-9648).

In embodiments, the disclosure provides compounds, polymer compositions,articles, and methods for making and using the compounds and polymershaving a core having an aromatic center and annulated fused thiophenes.

In embodiments, the disclosure provides a compound having an aromaticcenter and at least two annulated fused thiophenes on opposite sides ofthe center, and a method of making the compounds as defined herein.

In embodiments, the disclosure provides a polymer or copolymercomposition having a core comprising an aromatic center and at least twoannulated fused thiophenes, and further comprising one or more aromaticor heteroaromatic substituent (such as -G₁- or -G₁-G₂-G₁-) situatedbetween an adjacent core.

In embodiments, the disclosure provides articles having polymer orcopolymer compositions having an aromatic center and annulated fusedthiophenes.

In embodiments, the disclosure provides a polymeric or copolymericcomposition, and articles thereof prepared by any of the processes asdefined herein.

In embodiments, the disclosure provides an article or deviceincorporating the polymer, copolymeric, or polymer article as definedherein.

The disclosed compositions, articles, and methods can be used to preparemany different electro-optical devices, for example, OLEDs, OFETs,OTFTs, and like devices as disclosed, for example, in J. Am. Chem. Soc.,2008, 130, 13202-13203.

In embodiments, the disclosure provides α-, α′-un-substituted five-ringfused heteroaromatic compounds having a core structure as embodied, forexample, in the compound of formula 2 and 2′ in FIG. 4 and syntheticmethods for making the compounds. The three ring core starting materialsand their polymers are known (see Hebert, M., et al., Preparation of2,3-[di(2-thienyl)butane-2,3-diol and 4,8-dimethylbenzo[1,2-b;4,5,-b′]dithiophene,” Comptes Rendus (1971), supra.).

In embodiments, the present disclosure provides methods for making thecompound of formula 2a in FIG. 6 of this class of α-, α′-un-substitutedfive-ring fused heteroaromatic compounds. With such heteroaromaticcompounds available having the general structure of formula 2, thepreparation of the semiconductor polymers having monomers or co-monomersof the general structure of formula 4 and 5 as shown in FIG. 7 are alsodisclosed and demonstrated. The synthesis and characterization of thistype of semiconductor polymer, for example, of the structure of formula4a in FIG. 8 is demonstrated.

In embodiments, the disclosure also provides organic semiconductingpolymers containing a fused aromatic repeat unit, for example, compoundsof the formula 4 and 5 in FIG. 7.

In embodiments, the disclosure also provides methods for making thecompound of formula 2a of this α-, α′-un-substituted five-ring fusedheteroaromatic as shown in FIG. 6. Compound 2a and its precursors werepurified as described in the examples and characterized by ¹H NMR data.Compound 2a was prepared as a result of molecular modeling studies whichsuggested a potentially high mobility compound. A long alkyl side chain(“DC17” R═C₁₇H₃₅) was selected for the purpose of providing superiorcrystal packing properties and to in turn increase mobility and toprovide superior solubility for correspondingly superior solutionprocessing, such as purification, printing, and device fabricationapplications. Adapting the known (see commonly owned and assigned U.S.Pat. No. 7,838,623, issued Nov. 23, 2010) synthetic procedure used tomake the P2TDC13FT4 polymer illustrated in FIG. 3, the synthesis andcharacterization of the first example of this type of semiconductorpolymer, such as the polymer of formula 4a in FIG. 8 were demonstrated.These organic semiconductor polymer materials having a C₂ symmetricrepeat unit as shown in FIG. 7 have applications in, for example,organic electronics. Molecular modeling predicted that the polymer ofthe formula 4a in FIG. 8 should have superior mobility compared to ourprior high performance polymer, P2TDCXFT4, as discussed below. Solutionand solid UV-vis spectral data of the polymer of the formula 4aindicated that this is a likely high performance OTFT candidate.

The disclosed compounds, polymers, and preparative methods continue ourdevelopment effort in organic semiconductor materials and providenumerous preparative and performance advantages (see He, M.,“Preparation of fused thiophenes,” WO 2006031893; He, M., “Fusedthiophenes, methods for making fused thiophenes, and uses thereof,” U.S.Pat. Appl. Publ. US 2007161776; He, M., “Fused thiophene monomers,oligomers and polymers for use in electronic devices,” WO 2008106019;and He, M., “Fused thiophenes, methods for production and use inelectronic devices,” WO 2009123695). Compared to our prior four-ringfused thiophene small molecules (see commonly owned and assigned U.S.Pat. No. 7,838,623, issued Nov. 23, 2010), the existence of anadditional phenyl ring in this class of α-, α′-un-substituted five-ringfused heteroaromatics having a core structure of the formula 2 in FIG. 4extends the conjugation and may increase device performance. Comparisonof small molecule organic electronic components indicates, in general,that a greater number of fused phenyl rings in similar structuresincreases mobility. The fused thiophene polymers disclosed in commonlyowned and assigned WO2008/106019 (supra.) were synthesized by Stillecoupling between a dibromo fused thiophene monomer and a di-tinnon-fused aromatic monomer (or a vinyl di-tin monomer). Some advantagesof the disclosed compounds, polymers, and preparative methods arediscussed below.

Similar to our prior high performance β-, β′-alkyl substituted fusedthiophene polymers (FT4-FT7 polymers) (see Fong, H. H.,“Tetrathienoacene Copolymers As High Mobility, Soluble OrganicSemiconductors,” J. Am. Chem. Soc., (2008), 130(40), 13202-13203), a C₂symmetric repeat unit semiconductor polymer containing these α-,α′-un-substituted five-ring fused heteroaromatics as shown in FIG. 7 arepredicted, using modeling, to have high device performance, yet theywill probably provide different electronic properties due to theexistence of the center fused phenyl ring.

Using the method shown in FIG. 4, synthesis of these α-,α′-un-substituted five-ring fused heteroaromatics was achieved. Thefirst member of this α-, α′-un-substituted five-ring fusedhetero-aromatics, compound (2a), was synthesized by this method and waspurified and characterized as shown in FIG. 6. Compound 2a is expectedto have higher mobility than that of DC17FT4 since published examplesindicate that the substitution of thiophene rings by phenyl rings infused aromatics increases mobility significantly (Anthony, J.,“Functionalized acenes and heteroacenes for organic electronics,”Chemical Reviews (US), (2006), 106(12), 5028-5048). This is consistentwith our modeling data.

Semiconductor polymers containing these α-, α′-un-substituted five-ringfused heteroaromatics in FIG. 7 can be synthesized following our priormethod to make the high performance β-, β′-alkyl substituted fusedthiophene polymers (see Fong, H. H., supra.).

The solubility and solid state packing of these semiconductor polymersof formulas 4 and 5 in FIG. 7 can be modified using the disclosedflexible synthetic method to vary the length of alkyl side chain R₁, butalso to vary the length of alkyl side chain R₂.

A potential high mobility polymer of formula 4a in FIG. 8 wassynthesized and characterized. Modeling results indicated that that thepolymer of formula 4a should have superior mobility and superiorstability compared to our prior high performance polymer, P2TDC17FT4. A69 nm red shift from the solution maximum absorption to the solid-statemaximum absorption of this polymer suggested that this polymer is likelya high performance OTFT.

In embodiments, the disclosure provides methods to make α-,α′-un-substituted five-ring fused hetero aromatic compounds having C₂symmetry (FIG. 4). In embodiments, the disclosure also provides methodsto make their corresponding semiconducting polymers of formulas 4 and 5(FIG. 7). These organic semiconductor polymers have utility in organicelectronic devices. A recent publication highlighted the importance ofC₂ symmetry in the design of high performance organic thin filmtransistors (He, M., et. al., “Importance of C₂ Symmetry for the DevicePerformance of a Newly Synthesized Family of Fused-Ring Thiophenes,” J.Chem. Materials, (2010), 22(9), 2770-2779; see also Anthony, supra.).Accordingly, the presently disclosed five-ring fused hetero-aromaticcompounds of formula 2 in FIG. 4 were designed and prepared having C₂symmetry. Compound 2a of FIG. 6 can be expected to have higher mobilitythan that of DC17FT4 since literature examples indicate that with thesame number of fused rings, the substitution of thiophene rings byphenyl rings in fused aromatics increases mobility significantly(Anthony, supra). Since the compound of formula 2a has one more ring(i.e., an additional aromatic for a total of five fused rings) thanDC17FT4, it is expected to be more highly conjugated than DC17FT4. Thisexpectation was supported by comparing their respective UV-vis spectra(FIG. 10). While others have been interested in synthesizing this classof symmetric five-ring fused heteroaromatics (Kastler, M., et al., “Highperformance solution processible semiconductor based ondithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene,” WO 2010000670),there has been no reported synthesis of these α-, α′-un-substitutedfive-ring fused heteroaromatics of the formula 2 in FIG. 4. An initialattempted synthetic route to these α-, α′-alkyl substituted five-ringfused heteroaromatics of formula 3a as shown in FIG. 9 protected the α-,α′-position by alkyl chains to presumably facilitate the formation oftwo thiophene rings in the last ring closure step. However, severalattempts to accomplish the final ring closure step showed that thetarget compound of formula 3a was either not formed or formed only as aminor product in less than about 10% yield in an inseparable crudemixture. Since the final ring closure reaction shown in FIG. 9 wasunsuccessful, it was surmised that the construction of this α-,α′-un-substituted five-ring fused hetero aromatic might be accomplishedfrom inside-out. That is, the interior three fused ring including phenylring could be constructed first, and then the two peripheral fusedthiophene rings could be added. The general synthetic route using thisapproach is shown in FIG. 4. Compound of the formula 2a was preparedaccording to the route shown in FIG. 6. A pure compound of the formula2a was obtained in an overall isolated yield of about 15%. With theseα-, α′-un-substituted five-ring fused hetero aromatic compoundsavailable, a known procedure of bromination using NBS of the compound offormula 2a to form the polymer precursor of formula 3 (step 1 in FIG. 7)should be successful (Fong, H.-H., “Tetrathienoacene Copolymers As HighMobility, Soluble Organic Semiconductors,” J. Am. Chem. Soc., (2008),130(40), 13202-13203). Stille Coupling of precursor structure 3 with adi-tin compound (step 2 in FIG. 7) should readily form the desiredsemiconductor polymers containing the α-, α′-un-substituted five-ringfused heteroaromatics of formulas 4 and 5. By using this approach it waspossible to prepare and characterize a potential high mobility polymerof the formula 4a shown in FIG. 8. Modeling studies indicated that thepolymer of the formula 4a should have better mobility and thermalstability compared to our prior high performance polymer, P2TDCXFT4, asindicated by the Hole Reorganization Energy based on the repeat unit ofboth polymers. The structures of different fused aromatics were rankedfrom the lowest Hole Reorganization Energy (the highest mobility) to thehighest Hole Reorganization Energy (the lowest mobility) in the Marcusmodel discussed below. These modeling results showed that Model Compound9 for polymer 4a in the accompanying FIG. 14 Table 1 has a lower HoleReorganization Energy than Model Compound 19 for our prior highperformance polymer, P2TDCXFT4. The results suggest that the polymer offormula 4a should have a better mobility than our prior high performancepolymer, P2TDCXFT4. The slightly lower Hole Reorganization Energy inModel Compound 9 than that of Model Compound 10 indicates the importanceof the C₂ symmetry.

FIG. 10 shows exemplary UV-vis spectra for compounds of FIG. 8 of theformula 2a: DC17PhFT2FT2 (1010) (solid line) having an β-, β′-C₁₇H₃₅substituents of the formula:

and the known DC17FT4 (1020) (dotted line) having an β-, β′-C₁₇H₃₅substituents of the formula:

both measured in CH₂Cl₂. The shift in wavelength indicates that compound2a (1010) has greater conjugation than DC17FT4 (1020) attributable tothe added center fused phenyl ring. FIG. 11 shows examples of solution(1100) and solid (1120) UV-vis absorption spectra of the semiconductingpolymer of formula 4a in FIG. 8. The observed red shift of about 69 nmfrom the solution maximum absorption to the solid-state maximumabsorption for this polymer indicates that this polymer is most likely ahigh performance OTFT.

In embodiments, the disclosure provides a compound of the formulas 2,2′, 3 or 3′,

where R₁ and R₂ are independently selected from hydrogen, and asubstituted or unsubstituted, branched or unbranched, (C₁₋₄₀) alkyl, ora salt thereof, or mixtures thereof.

The compound of the formula 2, 2′, 3, or 3′ can be, for example,

or a salt thereof, or mixtures thereof.

The compound of the formulas 2a, or 2b can be, for example:

or a salt thereof, or mixtures thereof.

In embodiments, the disclosure provides a polymer of the formula 4, 4′,5, or 5′,

or a salt thereof, or mixtures thereof, where, for example,

n can be an integer from about 3 to about 30,

R₁ and R₂ can be independently selected from hydrogen, and a substitutedor unsubstituted, branched or unbranched, (C₁₋₄₀) alkyl,

G₁ and G₂ are divalent, substituted or unsubstituted, aromatic orheteroaromatic groups and can be each independently selected from, forexample,

or like groups, and combinations thereof, where R² can be independentlyselected from hydrogen, and a substituted or unsubstituted, branched orunbranched, (C₁₋₂₀) alkyl, and s is an integer of 0 to from 4.

The polymer of the formula 4, 4′, 5, or 5′, can be, for example,

where n, R, R₁, R₂, R₂, G₁, and G₂ are as defined herein, or a saltthereof, or mixtures thereof.

The polymer of the formula 4a can be, for example,

where n can be an integer from about 3 to about 30, or a salt thereof,or mixtures thereof.

In embodiments, the polymer of the formula 4a can have a mobility of,for example, from about 0.0192 to about 0.0772 cm²/V·s, includingintermediate values and ranges.

In embodiments, the disclosure provides a method of making the compoundof the formula 2, 2′, 3 or 3′, or a salt thereof, or mixtures thereof,comprising:

contacting a compound of the formula:

and at least two equivalents of a dihalogen or other suitablehalogenation reagent, such as NBS, to respectively provide a compound ofthe formula:

where X is halogen;

α, α′-diacylating the resulting halogenated product to respectivelyprovide a compound of the formula:

bis-annulating the resulting diacylated product with a β-thiol acetateester to respectively provide a five-ring core compound of the formula:

where —R₃ is (C₁₋₄)alkyl;

hydrolyzing the resulting diester to respectively provide a diacidcompound of the formula:

decarboxylating the resulting diacid to respectively provide an α,α′-unsubstituted compound of the formula 2 or 2′:

and

contacting the compound of the formula 2 or 2′ with a dihalogen torespectively provide a compound of the formula 3 or 3′:

In embodiments, the α, α′-diacylating can alternatively be accomplishedin two steps with an aldehyde equivalent to provide an intermediate ofthe formula:

followed by oxidation instead of directly reacting with an acyl halide.

In embodiments, the disclosure provides a method of making a polymer ofthe abovementioned formulas 4 or 5, comprising for example:

contacting the dihalogen compound of formula 3:

where X is halogen, with a di-tin compound of the formula(R)₃Sn-G₁-Sn(R)₃ or of the formula (R)₃Sn-G₁-G₂-G₁-Sn(R)₃ torespectively form a compound of the formulas 4 or 5:

The dihalogen compound of formula 3 can be of the formula 2b:

(R)₃Sn-G₁-Sn(R)₃ can be, for example, a bis-thiophene of the formula:

andthe polymer of the formula 4 can be of the specific formula 4a:

In embodiments, the disclosure provides a device comprising at least onepolymer of the formulas 4 or 5:

where R₁ can be, for example, CH₃, R₂ can be, for example, C₁₇H₃₅, G₁and G₂ can be, for example, independently selected from -(thiophene)-,-(thiophene)₂-, -{(beta-C₁₇-substituted-thiophene), or-{(beta-C₁₇-substituted-thiophene)₂- and n is 5 to 20. In embodiments,R₁ can alternatively be —OR₁ as defined herein.Molecular Design: Marcus Model

Charge transport properties depend on the degree of ordering of the πsystem or molecular ordering in the solid state as well as the densityof chemical impurities, structural defects such as grain size anddislocations, or combinations thereof (see Garnier, F., et al., Science(1994) 265, 1684; Katz, H. E., J. Mater. Chem., (1997) 7, 369; andHorowitz, G., Adv. Mater. (1998) 10, 365). At the electronic level, twoof the more significant factors that control transport properties inorganic conjugated materials are the interchain transfer integral β, andthe reorganization energy λ. The transfer integral expresses the ease oftransfer of a charge between interacting chains. The reorganizationenergy term describes the strength of the electron-phonon coupling. Itis proportional to the geometric relaxation energy of the chargedmolecule over the individual neutral unit. In the context ofsemi-classical electron-transfer theory, the electron-transfer (hopping)rate can be expressed by Eq. (1) from Marcus theory in simplified termsas:

$\begin{matrix}{k_{et} = {\frac{4\pi^{2}}{h}\frac{1}{\sqrt{4\pi\; k_{B}\lambda\; T}}\beta^{2}{\mathbb{e}}^{- \frac{\lambda}{4k_{B}T}}}} & (1)\end{matrix}$where T is the temperature, λ is the reorganization energy, β is thetransfer integral, and h and k_(B) are the Planck and Boltzmannconstants (see Marcus, R. A., Rev. Mod. Phys. (1993) 65, 599).

To characterize the relative influence of both parameters to the chargetransport rate, replace Eq. (1) by a simpler expression (2):

$\begin{matrix}{k_{et}^{simple} = {\frac{1}{\sqrt{\lambda}}\beta^{2}{\mathbb{e}}^{- \lambda}}} & (2)\end{matrix}$Eq. (2) describes a two variable function and allows assessment of therelative importance of the variables on the charge transfer rate, andhence mobility. The results in FIG. 12 depict how mobility varies as afunction of the reorganization energy when five different values of thetransfer integral are considered (i.e., calculated mobility (μ) over atransfer integral range from about 0.4 eV to about 2 eV). These are veryrealistic transfer integral values for a small molecule organicsemiconductor. Deng calculated the transfer integral for pentacene withherringbone packing (Deng, W.-Q., et al., J. Phys. Chem. B, (2004), 108,8614-8621). Their results of calculated mobility using Eq. (1) yieldedreasonable agreement with the mobilities measured for a single crystal.The maximal values of the transfer integrals for different directions incrystalline pentacene were between 0.2 eV and 0.32 eV. A wider range wasused in the present calculations to include optimal cases and beyond.From FIG. 12, it is apparent that the difference in mobility fordifferent transfer integrals is only significant for small values of thereorganization energy. A large increase in the transfer integral doesnot yield a significant variation in the mobility, unless thereorganization energies are small. This implies that any optimization ofthe mobility should start with the design of a molecule with very lowreorganization energy.Modeling Details

The reorganization energy includes two contributions that are associatedwith charge hopping. One is introduced by the geometric changes withinthe single molecule, and is denoted the internal part. The second onearises from the re-polarization changes of the surrounding medium. Thislast contribution will be neglected in the evaluation of thereorganization energy. Such an approximation is valid since nosignificant solvent reorganization occurs during the charge transfer inthe condensed phase. The reorganization energy for hole transfer, asconsidered in Eq. (1), can be estimated by Eq. (3) as the sum of twoparts:λ=λ₀+λ₊=(E* ₀ −E ₀)+(E* ₊ −E ₊)  (3)

FIG. 13 illustrates the calculation of the reorganization energy. Foreach molecule, the geometry is optimized using quantum mechanics forboth neutral and ionic states. Consequently, the basic hopping step in amolecular wire is defined by four energies: E₀ and E₊ represent theenergies of the neutral and cation species in their lowest energygeometries, respectively, while E*₀ represents the energy of the neutralspecies having the optimized geometry of the cation and E*₊ representsthe energy of the cation species having the optimized geometry of theneutral species. The quantum mechanics calculations to determine theseabove mentioned quantities used the experimentally parameterizedHamiltonian PM6 implemented in VAMP® (Accelrys Software, Inc.) Pentacenewas used as a reference to validate the Hole Reorganization Energy (RE)calculations. Experimental data for pentacene RE is about 0.12 eV,compared to 0.114 eV from VAMP. FIG. 14 lists in Table 1 the HoleReorganization Energies for selected molecules having some structuralresemblance to the repeat unit (Model Compound 9) of the polymerproposed as a good candidate for semiconductor applications and polymer(P2TDC13FT4, Model Compound 19 in Table 1). The monomer of the suggestedpolymer has a Hole Reorganization Energy of 0.199 eV compared to 0.243eV for P2TDC13FT4. This corresponds to about an 18% improvement of theHole Reorganization Energy.

Based upon other known and related compounds and polymers, the disclosedcompounds and polymers are expected to have excellent organicsemiconductor properties, such as increased thermal stability andoxidative stability, and increased ease of manufacture based onincreased solubility and increased synthetic efficiency, such as fewersteps.

Advantages of the present preparative methods include, for example, therelatively straightforward path to a variety of new polymers andcopolymers, especially those polymers having a core member having anaromatic center and at least two fused thiophenes annulated thereto. Thedi-tin fused thiophene monomer compounds are convenient to preparebecause of their high crystallinity and solubility characteristics.

The disclosed preparative method can be extended to any fused aromaticdi-tin monomer. The disclosed polymer or copolymer preparative methodscan be extended to the synthesis of conjugated polymers having a likecore including an aromatic center and at least two fused thiophenesannulated thereto.

EXAMPLES

The following examples serve to more fully describe the manner of usingthe above-described disclosure, and the best modes contemplated forcarrying out various aspects of the disclosure. It is understood thatthese examples do not limit the scope of this disclosure, but rather arepresented for illustrative purposes.

Experimental Details for Compound 2a (FIG. 6) and Polymer 4a (FIG. 8)Example 1 Synthesis of Compound C

To a cloudy solution of compound B (0.28 g, 1.28 mmol) in mixed solventsof glacial HOAc (20 mL) and CH₂Cl₂ (4 mL) in darkness, 0.92 g (5.8 mmol)of Br₂ was added. The resulting mixture was stirred at room temperaturefor 3 days. Ice-cooled aqueous NaOH solution was added. Methylenechloride was then removed under reduced pressure to yield a solutioncontaining a precipitate. The precipitate was then collected byfiltration and washed successively with aqueous sodium carbonatesolution, water, MeOH, and CH₂Cl₂. Compound C was collected as a greyishsolid (0.68 g, 68%). ¹H NMR (300 MHz, d₈-THF): δ 3.10 (s, 6H). GC/MS535[M+].

Example 2 Synthesis of Compound D

To a cloudy solution of Compound C (1.60 g, 3.00 mmol) in anhydrous THF(55 mL) at −78° C., 2.66 mL of n-BuLi solution in hexane (2.25 M) wasadded dropwise under a nitrogen stream. This was stirred at −78° C. forabout 3 hours until only a small amount of starting materials could bedetected by GC/MS. To this mixture was quickly added a solution of 1.77g (6.59 mmol) of n-C₁₇H₃₅CHO in anhydrous THF (8 mL). The solution waswarmed to room temperature slowly overnight. It was then quenched withwater. After removing THF, a light yellowish solid was collected byfiltration and washed with water and then MeOH. Column chromatography ofthis solid yielded 1.05 gram (38%) of Compound D in about 90% purity. ¹HNMR (300 MHz, d₈-THF): δ 5.14 (t, 2H), 3.11 (s, 6H), 1.82 (p, 4H),1.70-1.43 (m, 64H), 0.89 (t, 6H).

Example 3 Synthesis of Compound E

To a solution of Compound D (5.83 g, 6.38 mmol) in refluxing acetone(200 mL), 19.1 mL of Jones Reagent was added dropwise. The resultingmixture was refluxed overnight. After cooling to about 25° C., agreenish precipitate was collected and it was mixed with hot aqueous 4NHCl solution and stirred for about 3 hours. This solid was furtherwashed by acetone to yield 4.42 gram (75%) of Compound E. ¹H NMR (300MHz, d₈-THF): δ 3.22 (s, 6H), 3.17 (t, 4H), 1.79-1.42 (m, 60H), 0.89 (t,6H).

Example 4 Synthesis of Compound F

To a stirred solution of Compound E (4.42 g, 4.86 mmol), K₂CO₃ (6.72 g,48.6 mmol) and a catalytic amount of 18-crown-6 were added in DMF (50mL). Ethyl mercaptoacetate 1.17 g (9.72 mmol) was added dropwise at60-70° C. This mixture was stirred for three days. The mixture was thenpoured into water (400 mL) and the precipitate that formed wascollected. The light yellowish precipitate was washed with water andthen by MeOH (3.70 g, 80%). ¹H NMR (300 MHz, CD₂Cl₂): δ 4.38 (q, 4H),3.20 (t, 4H), 2.89 (s, 6H), 1.78 (p, 4H), 1.54-1.08 (m, 62H), 0.87 (t,6H).

Example 5 Synthesis of Compound G

A solution of a mixture of Compound F (2.89 g, 3.04 mmol), LiOH (10% inwater, 8.0 mL), THF (150 mL), water (10 mL), methanol (10 mL), and acatalytic amount of tetrabutyl ammonium iodide, was refluxed for about24 hr. The mixture was then cooled to about 25° C. and most of THF andMeOH were removed. The resulting cloudy solution was then poured intowater (50 mL). Aqueous hydrochloric acid (4N, 200 mL) was added to theaqueous residue. Solid was filtered and washed with water (3×300 mL).The light yellow solid of Compound G was washed with methanol (150 mL)and dried under vacuum overnight (2.64 g, 97%).

Example 6 Synthesis of Compound 2a

A mixture of Compound G (1.38 g, 1.54 mmol), Cu₂O (0.100 g) and glycine(0.100 g) in tetraethyleneglycoldimethylether (40 mL) was heated to220-230° C. in a flask fitted with drying tube. The reaction wasterminated after 3 h. The hot reaction mixture was filtered as quicklyas possible to remove the copper oxide or any other solid residue. Thefiltered solution was then cooled to about 25° C. and gave a pale yellowprecipitate after short-path column chromatography purification. Thispale yellowish solid was recrystallized from hexane to give the desiredproduct, compound 2a (1.01 g, 81% yield) as a pale yellowish solid. ¹HNMR (300 MHz, CD₂Cl₂): δ 7.23 (s, 2H), 2.92 (s, 6H), 2.83 (t, 4H), 1.84(p, 4H), 1.56-1.10 (m, 56H), 0.89 (t, 6H).

Example 7 Synthesis of Compound 2b

To a cloudy solution of Compound 2a (0.75 g, 0.93 mmol) in 50 mL ofCH₂Cl₂, a solution of 0.364 g (2.04 mmol) of NBS in 25 mL DMF was added.The resulting solution was stirred at about 25° C. for 2 days. Thisreaction was quenched by adding water (1 mL). Methylene chloride wasremoved under reduced pressure and 150 mL of water was added. A paleyellow precipitate formed and was collected, then washed with water andthen MeOH. The material was recrystallized from toluene (20 mL) to givecompound 2b (0.87 g, 97% yield) as a pale yellow solid. ¹H NMR (300 MHz,CD₂Cl₂): δ 2.83 (s, 6H), 2.83 (t, 4H), 1.79 (p, 4H), 1.50-1.18 (m, 56H),0.87 (t, 6H).

Example 8 Synthesis of Polymer 4a

Compound 2b (440.9 mg, 0.457 mmol) and1,1′-[2,2′-bithiophene]-5,5′-diylbis[1,1,1-trimethylstannane] (225 mg,0.457 mmol) were dissolved in toluene (25 mL) in a flask. Nitrogen wasbubbled through this flask for a several minutes. Tetrakis(triphenylphosphine) palladium(0) (52.8 mg, 0.0457 mmol) was added tothis mixture. The mixture was refluxed under nitrogen for 16 hr thenpoured into a methanol (300 mL) and concentrated hydrochloric acid (5mL) solution and stirred for 16 hr at about 25° C. The precipitate wasfiltered and Soxhlet extracted sequentially with acetone and then hexane24 h each. The collected dark-red polymer was dried in vacuum to yield0.34 grams (76.6%) of polymer 4a (λ_(max) in CH₂Cl₂ solution=465 nm,λ_(max) in thin film=534 nm). GPC (1,2,4-trichlorobenzene) Mn=8,000,Mw=10,300; and PDI=1.28 relative to polystyrene standards.

Example 9 Device Fabrication and Characterization

All top-contact bottom-gate transistors using polymer 4a as an organicsemiconducting channel were fabricated in air. Si<100> wafers were usedas gate electrodes with silicon dioxide as the gate dielectric. OFETdevices based on polymer 4a in 1,2-dichlorobenzene were fabricated onHMDS vapor treated Si/SiO₂ wafers. Polymer films were annealed at 150°C. Measured mobilities ranged from 0.0192 to 0.0772 cm²N s. On/off ratioranged from 10⁴ to 10⁵.

The disclosure has been described with reference to various specificembodiments and techniques. However, it should be understood that manyvariations and modifications are possible while remaining within thescope of the disclosure.

1. A compound of the formulas 2a, or 2b:

or a salt thereof, or mixtures thereof.
 2. A method of making a compoundof the formula 2, 2′, 3, or 3′

where X is halogen R₁ and R₂ are independently selected from hydrogen,and a substituted or unsubstituted, branched or unbranched, (C₁₋₄₀)alkyl, or a salt thereof, or mixtures thereof, comprising: contacting acompound of the formula:

and a halogenating agent to respectively provide a compound of theformula:

where X is halogen; α, α′-diacylating the resulting halogenated productto respectively provide a compound of the formula:

bis-annulating the resulting diacylated product with a β-thiol acetateester to respectively provide a five-ring core compound of the formula:

where —R₃ is (C₁₋₄)alkyl; hydrolyzing the resulting diester torespectively provide a diacid compound of the formula:

decarboxylating the resulting diacid to respectively provide an α,α′-unsubstituted compound of the formula 2 or 2′:

and contacting the compound of the formula 2 or 2′ with a halogenatingagent to respectively provide a compound of the formula 3 or 3′: